In a randomized trial, patients receiving rocuronium followed by a saline flush had an earlier onset of neuromuscular blockade than those receiving rocuronium alone.

Reliable, rapid onset of neuromuscular blockade is critical for successful emergency rapid sequence intubation (RSI). Rocuronium has a slower onset than succinylcholine. The effect of a large-volume saline flush on rocuronium’s onset time is not known.

Researchers at a Japanese military hospital randomized 48 healthy non-obese patients to rocuronium (0.6 mg/kg IV) with or without a 20 mL saline flush. Anesthesia was induced with standard infusions of propofol and remifentanil. All medications were administered through a 20- or 22-gauge catheter in a large-caliber forearm vein.

The average onset of neuromuscular blockade (defined as ≥95% muscle twitch depression) was 15 seconds shorter in the saline-flush group than the placebo group. The recovery phase was prolonged by nearly 9 minutes in the saline-flush group.

Comment:
Once RSI is planned and drugs are administered, rapid paralysis is paramount. Although the dose of rocuronium used in this study is lower than that used for emergency airway management, there is no reason to believe a saline flush would not have the same effect with the RSI dose, and this simple additional step could make the onset of action as rapid as that with succinylcholine. The longer recovery phase is irrelevant for emergency physicians, and I see no downside to saline flush with rocuronium RSI. Time permitting, administration of rocuronium should be followed by a saline flush.